A power line communication system ("PLC") typically operates by superimposing a modulated carrier frequency on the AC signal carried on a power line. A basic PLC system consists of a transmitter unit capable of adding the communication signal to the AC power line signal and a receiver unit capable of separating the communication signal from the AC power component signal.
In an ideal PLC system, the output signal of the receiver is a perfect copy of the signal which was introduced to the transmitter. That is, any signals (i.e., noise) which may impinge upon the system from a source other than the transmitter are ignored by the receiver. The ideal PLC system should furthermore not become a source of noise either through direct transmission or by radiation.
In previous circuits, PLC systems has been used for relatively low carrier frequencies of 160 Kilohertz (KHz) to 455 Kilohertz (KHz). Some may utilize a frequency as high as 1.5 Megahertz (MHz).
The AC power line may broadcast the communication signal. This creates noise which may interfere with other communication signals. If the communication signal strength is too low, the signal will be overpowered by the level of noise on the line. If the communication signal is strong and is a very high frequency, the power line may begin to radiate and thus violate government regulations regarding interference and harmful radiation levels.